Impact of phosphonium-based ionic liquids-modified carbon nanotube on the microwave absorbing properties and crystallization behavior of poly(vinylidene fluoride) composites

Poly(vinylidene fluoride) (PVDF)/multi-walled carbon nanotube (CNT) conducting composites were prepared using two procedures: melt mixing and dry-mixing in a ball-mill. Alkyl-phosphonium – based ionic liquids were also employed as noncovalent modifier for CNT. The composites prepared by dry-blending displayed higher conductivity. The β/γ crystal formation in the PVDF matrix was induced by CNT modified with ionic liquids using melt blending approach, as indicated by Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) analysis. The composite prepared by melt mixing, loaded with 0.5 wt% of CNT modified with trihexyl-(tetradecyl) phosphonium bistriflimide and 3 mm thick displayed outstanding microwave absorbing properties with minimum reflection loss (RL) of −13.6 dB at 11 GHz. Moreover, broad bandwidth (>3.1 GHz with microwave attenuation higher that 90%) and minimum RL of −39 dB were achieved using triple layered structure with PVDF/CNT composites with 1 mm thickness stacked together in appropriate arrangement. • PVDF/CNT with outstanding electrical conductivity prepared by Ball-milling approach. • Phosphonium-based ionic liquids as efficient compatibilizing for PVDF/CNT nanocomposites. • CNT/ionic liquid hybrids induce the formation of β-crystal phase in PVDF composites prepared by melt blending. • Outstanding microwave absorbing properties achieved with multi-layered PVDF/CNT and PVDF/CNT/IL composites.